The invention relates to agricultural pest control. More specifically, the invention concerns use of natural product derived microemulsions to control agricultural pests, in particular plant nematodes.
The negative impact of infestation by pests on agricultural production is well-known. Damage worldwide due to nematode infestation alone is estimated at $78 billion per year. Other sources of infestation include bacterial, fungal, and insect pathogens. Assault on these infestations has taken the form of use of synthetic pesticides derived from petroleum, use of natural predators, and use of compounds derived from natural sources, such a pyrethrins. No completely satisfactory pesticide which is specific, effective, and not harmful to the environment has been found. Thus, there is a considerable need for finding improved pesticides.
With regard to previous compositions related to those of the present invention, the effect of fatty acids on a particular species of plant nematodes (Meloidogyne javanica) has been described by Sitaramaiah, K., et al., Indian J. Nematol. (1977) 7:58-65. Formic, acetic, propionic and butyric acids were tested. The effect of a collagenolytic/proteolytic enzyme secreted from Bacillus cereus after induction by collagen on this plant nematode species has also been reported by Sela, S., et al., Eur. J. Plant Pathol. (1998) 104:59-67. The enzyme was effective to digest collagen from cuticles of second stage juveniles. U.S. Pat. No. 5,698,592 describes compositions for the control of plant infective nematodes using fatty acid compounds which compositions are microemulsions containing C8-C14 fatty acid esters. The esters were prepared synthetically and the nature of the microemulsions is not described.
Fatty acid or oil compositions have also been described for other purposes, including the use of a vegetable oil/mineral salt broth fermented by yeast as an emulsifier in the food industry, as described in U.S. Pat. No. 4,810,507; the use of a mixture of an oleate derivative, a lower alkanol, and an inert diluent as a pharmaceutical penetration agent, as described in U.S. Pat. No. 4,863,970; and the use of a solution of oleic acid, acetone, and ammonium hydroxide in water as a treatment for athlete""s foot, as described in U.S. Pat. No. 4,172,888. Unsaturated lipid compounds containing polar head groups, including oleates, are described as cell-envelope disordering compounds.
The use of microbial infection to control nematode infestation in plants was described in U.S. Pat. No. 5,264,210. PCT Application WO98/59036 describes compositions for the control of nematode infestation using metabolites from fungi. In some cases, the fungi are cultured in media which include vegetable oil and the compositions may include surfactants.
U.S. Pat. Nos. 5,674,897; 5,698,592; and U.S. Pat. No. 6,124,359, all assigned to Mycogen describe microemulsions containing fatty acid esters for use as nematocides. These fatty acid esters are of C8-C-14 fatty acids and they do not appear to include glyceride esters. Various other patents disclose the use of alkoxylated materials and other emulsifiers for use in pesticides or herbicides intended for application to plants. These include U.S. Pat. Nos. 4,975,110 and 5,098,467 to Safer; U.S. Pat. No. 5,827,522 to Troy and U.S. Pat. No. 6,093,681 to Monsanto. In addition, U.S. Pat. No. 5,362,707 assigned to Rhone Poulenc describes the use of xe2x80x9csuspoemulsionsxe2x80x9d as vehicles to apply pesticides with solid active ingredients (having melting points  greater than 45xc2x0 C.) to plants.
It has not heretofore been appreciated that complexes containing a hydrophilic core, at least one monounsaturated fatty acid backbone, surfactants, and including a polyalkoxylene, (such as compositions containing a denatured lipase with long chain fatty acids or their derivatives) prepared in the form of a clear microemulsion are particularly effective in controlling pests in agricultural settings.
In addition, the formulation of agents employed for dispersal and penetration of active ingredients is useful as a carrier for plant nutrients, pesticides in general, herbicides, and other materials suitable for application to plants and is also useful as a topical drug delivery system.
A wide variety of carriers for active ingredients has been devised in both the pharmaceutical and agricultural arts. For example, drug delivery systems have included various forms of liposomes, various polymeric slow-release compositions, detergents which aid in penetration, and other excipients that affect the behavior of small molecules or proteins or other biological molecules that are considered to be the active ingredients. The formulation of the present invention, originally developed as a carrier for nematocides, has been found useful as a delivery system for pesticides in general, for plant nutrients, and for topical application of drugs as well. The carrier of the present invention is particularly effective in dispersing active ingredients over a wide area and in effecting penetration of these active ingredients through cell walls and membranes and is thus useful both in agricultural and pharmaceutical contexts.
The invention is directed to environmentally friendly but effective pesticides for use on plants. The pesticide can be prepared in a premixed concentrated form and then diluted for application to agricultural crops such as tomato, potato, pineapple, and any other target crop which is subject to pest infestation. The composition is a microemulsion that appears clear to the naked eye. Indeed, the turbidity of the microemulsion must be quite lowxe2x80x94when measured with a turbidometer, the turbidity should be less than about 3 NTU, preferably less than 2.5 NTU, more preferably less than 1 NTU. The clear microemulsion will contain as active ingredient a complex which comprises a moiety having a hydrophilic core to which is covalently bound at least one backbone of a monounsaturated fatty acid of C16-C20, preferably an oleic acid backbone. As used herein, xe2x80x9cbackbonexe2x80x9d of a fatty acid refers only to the carbon chain and does not include the carboxyl group oxygens. Typically, this core is a saccharide, such as sucrose, glucose, or a more complex saccharide esterified with one or more oleic acid or similar residues. The complex moiety may also be formed from the association of a denatured lipase and a long chain monounsaturated fatty acid or its esters. The complex will also contain detergents and some form of polyoxyalkylene, such as polyoxyethylene. The polyoxyalkylene may be associated directly with the moiety described above or may be included in a separate portion of the complex.
Thus, in one aspect, the invention is directed to the active ingredient of the pesticide, which is a complex consisting essentially of at least one C16-C20 monounsaturated fatty acid or ester thereof associated with a denatured lipase, an anionic surfactant blend, a microemulsion surfactant blend, and polymers which are polyoxyalkylene polymers. The polyoxyalkylene is supplied by providing alkyoxylated linear alcohols of C9-C11. In another embodiment, the active ingredient is a complex consisting essentially of a saccharide esterified with at least one monounsaturated C16-C20 fatty acid and the anionic surfactant blend, a microemulsion surfactant blend, and polymers which are polyoxyalkylene polymers. The polyoxyalkylene polymers are preferably provided by derivatizing the saccharide.
In another aspect, the invention is directed to a pesticide premix consisting essentially of a homogenized mixture of the components set forth above. Further, the invention is directed to the diluted form of the premix and to a method to control agricultural pests which comprises applying the pesticidal dilution to an agricultural crop.
The invention is further directed to methods to prepare these pesticide compositions.
Specifically, the carrier comprises at least three components. The first component is at least one linear alcohol of 7-12 C, preferably 9-11 C, which is polyalkoxylated. The second component is at least one surfactant which is designed to promote formation of microemulsions. The third component is at least one anionic surfactant. If desired, a disproportionate amount of a linear alcohol of 11-12 C with a high degree of polyalkoxylation may also be included. The components should be mixed in a particular order in order to ensure maximum effectiveness.
Thus, in another aspect, the invention is directed to a dispersant/penetrant which consists essentially of:
at least one linear alcohol of 7-12 C which linear alcohol is polyalkoxylated;
at least one surfactant that promotes microemulsion; and
at least one anionic detergent.
The invention is also directed to agricultural and pharmaceutical compositions which comprise at least one active ingredient (for example, the nematicide complex described above) and the dispersant/penetrant compositions of the invention. In still another aspect, the invention is directed to methods to prepare and use these formulations.
The pesticide compositions of the invention are applied to crops or to fields or environments where pesticide control is desired in the form of clear microemulsions. The clarity appears to be important. Not only does the final composition need to appear clear to the naked eye, it should have a very low turbidity index when measured in a turbidometer. Preferably, the composition should be less than 3 NTU, more preferably less than 2.5 NTU, and still more preferably less than 1 NTU. Pure water has an NTU value of 0.3.
The compositions ultimately to be applied are prepared by diluting a premix which contains the active ingredient.
While not intending to be bound by any theory, it is believed that the active ingredient in the pesticide compositions in the invention is a complex comprising a moiety containing a lipophilic component and a hydrophilic portion which can be associated with an anionic surfactant. There are two embodiments of the active ingredient which share these characteristics.
Lipase/Fatty Acid Complexes
In one embodiment, lipases which can complex with triglycerides comprising fatty acids which contain a single double bond and which have maximal activity on fatty acid chain lengths of 8 carbons are employed. These have minimal enzymatic effects on esters of C18 fatty acids. In a preferred embodiment, the fatty acids which are present in the complexes of the present invention may have chain lengths of 16-20 carbons. More preferably, the chain length of the triglyceride-esterified fatty acid used in the composition is C18. The lipase may merely associate with the triglyceride and not hydrolyze it; indeed, in some compositions of the invention prepared from oils comprised primarily of oleate triglycerides, compositions which contain lipases derived specifically from Laetiporus sulphureus contain the same level of triglyceride as untreated oils. Moreover, lipases suitable for the compositions of the invention associate not only with triglycerides, but also with diglyceride and monoglyceride and other esterified forms of the fatty acids as well as with the free fatty acids themselves, provided they include fatty acids of 16-20, preferably 18 carbons in length.
Many of such lipases are of fungal origin. Since triolein is the primary storage oil of many fungi, certain fungal lipases are genetically designed not to degrade the naturally occurring triolein in the environment, but catalyze the degradation of other triglycerides with different fatty acid chain lengths. This would result in intact triolein, diolein, monolein and oleic acid in the environment of a fungal colony producing this type of lipase enzymes on a mixed fatty acid source. This type of lipase is relatively specific for 8-carbon fatty acids and will only hydrolyze C18 fatty acids to a limited extent. The enzyme attaches to the triglyceride containing oleic acid, recognizes the chain length, and releases the triglyceride only when suitable cleavable triglyceride is available. If not, the lipase will remain attached to the uncleavable triglyceride. Thus, when these lipases are coupled with a triglyceride consisting of C18 fatty acids, the lipase will attach, but not cleave the fatty acids from the glycerol.
It will be noted that in this embodiment, the hydrophilic core includes the oxygens of the carboxyl groups of the fatty acid residue; thus, the xe2x80x9cbackbonexe2x80x9d of the fatty acid is covalently bound to the hydrophilic core, which includes these oxygens as well as the lipase.
In order to stabilize the complex, it is preferred that the lipase portion of the complex be denatured. Thus, the complex, after formation, is treated, preferably by heating to a suitable temperature, to denature the lipase protein.
The complex can be prepared by utilizing purified preparations of suitable lipases preferably but not necessarily derived from fungal sources and permitting the lipase to associate with a fatty acid or fatty acid ester wherein the fatty acid backbone has the appropriate length (C16-C20) and the preferred amount of unsaturation (one double bond). The ester may be an ordinary ester such as a methyl, ethyl, ethylene glycol, propyl, or butyl ester, and the like, or, preferably, the fatty acid is esterified to glycerol either as a mono, di and preferably triglyceride. Triglycerides are readily available as components of vegetable oils, and thus vegetable oils constitute a preferred source, especially oils that contain high concentrations of trioleate, such as safflower or sunflower seed oil.
The complex, for use in the compositions of the invention must be denatured. The denaturation step is typically performed by heat, but other denaturing agents, such a chaotropic agents and adjustment of pH could also be used. The denaturation step is an essential one in preparing the resultant hydrophobic/hydrophilic complex.
Thus, for preparing these compositions, a vegetable oil, high in trioleate content is preferred. Such an oil is, for example, Optimum(trademark) Sunflower Oil, Optimum Quality Grains, Inc., Urbandale, Iowa. Other oil compositions which contain mono, di, or triglycerides of fatty acids of suitable length may also be used. The presence of a single double bond in the fatty acid is preferred. It should be emphasized that the trioleate must contain at least one monounsaturated fatty acid of 16-20 carbons in length, preferably 18 carbons, but this need not be the only fatty acid component of the oil. As long as substantial amounts of this fatty acid are present.
Oil sources include nonplant sources such as from fish or whales which would increase the carbon chain possibilities for monounsaturates from a range of C16-C20 to C16-C26. For forming the complex, suitable lipases can be obtained from plant, fungal, bacterial, and animal sources. One suitable lipase is wheat germ lipase. (Wheat germ lipase does not digest triolein.) Suitable fungi include Laetiporus sulphureus, Ganoderma spp, Mucor spp, Rhizopus spp, and Penicillium spp. Also available are lipases from fungi such as Candida spp and Aspergillus spp. Suitable bacteria include Pseudomonas spp, Rhizobium spp or Chromobacterium spp. Suitable animal sources include pigs, goats, sheep, and bovine sources. Lipases are also commercially available such as those obtainable from Valley Research Technologies, South Bend, Ind., which markets Validase 8000, a lipase commonly used in cheese-making. Of course, mixtures of individual lipases can be used. Typical lipases useful in the invention are those described by enzyme No. ECC 3.1.1.3 or CAS No. 9001.62-1.
A wide variety of lipase sources can thus be used. One such source is cheese itself and the various microorganisms used in its manufacture. It should be emphasized that because many cheeses have a high lipase content, such cheeses can be used in the formulation per se. The types of cheese that can be used constitute a wide variety, including cottage cheese, cream cheese, brie, mozzarella, Monterey Jack, Munster, blue cheese, cheddar, edam, gouda, Swiss, parmesan and romano. Particularly preferred is chevre which has a high moisture content and appears to be very high in lipase content, especially when fresh. Blue cheese and brie also have high contents of lipase. The bacteria and fungi that are used in the manufacture of these cheeses also are good lipase sources. These microorganisms include, prominently, S. lactus, S. cremoris, and S. thermophilus. 
In addition to these microorganisms, the ATCC web site provides an extensive list of microorganisms including many penicilia and kluyveromyces that produce lipase. There is an extensive list of fungi in general, and yeast in particular that produce lipase that is useful in the invention. Such organisms include Aspergillus oryzae, Aspergillus soyae, Sachromyces rouxii, Aspergillus flavus, Hansenula subpelliculosa, Zygo-sachromyces, Lactobacillus delbraeki, Rizous oligosporus, Neuraspura sitophila, and many others. In addition, a wide variety of yeasts, as listed in the American Type Culture Collection Catalog, current edition, incorporated herein by reference, lists multiple yeast genera which can be used as sources of lipase.
Finally, lipases are found in seeds of germinating plants, such as wheat, oats, corn, rice and rye, as well as plants where seeds contain substantial amounts of triglycerides, such as soy beans, safflower, canola, corn, cotton seed, sunflower, olive, walnuts, macadamia nuts, peanuts, and the like can be used as a source of lipase. Crude extracts can be used or the lipase can be purified to any desired extent. In these preparations, other stabilizing components, such as dextrin, may be included.
In general, the ester and lipase are mixed together in an aqueous environment for a sufficient time and at an appropriate temperature to permit complex formation. Typically, complex formation occurs over a period of several hours at slightly elevated temperatures. Typical conditions would be represented by periods of 10-40 hours at temperatures of 30-50xc2x0 C. Then the oil phase is recovered and subjected to treatment to denature the lipase, typically treatment using heat. Denaturing conditions vary depending on the components utilized, but typically such conditions would include treatment at 90-99xc2x0 C. for 5-20 minutes. In one manner of performing this step, the lipase is purified.
In one embodiment, to prepare the lipase/fatty acid or ester complex, above, the lipase may be supplied in the form of a culture filtrate from cultivation of a suitable fungus, such as those set forth above as suitable sources for the lipase. In this approach, the fungus is cultivated for a period of 10-30 days, preferably around 20 days, in a cultivation vessel forming a mycelium mat. Suitable nutrients are those typically appropriate for the cultivation of the particular species of fungus employed. After the incubation period, the culture fluid is separated from the mycelium. The separation may occur when the fungus is xe2x80x9cimmaturexe2x80x9d i.e., prior to the termination of growth phase or when the fungus is xe2x80x9cmaturexe2x80x9dxe2x80x94i.e., at the point where growth phase begins to level off. The culture fluid is filtered and then mixed with the oil (or other fatty acid ester) for an appropriate time period, such as 18-30 hours, preferably around 24 hours at 27-35xc2x0 C., preferably 33xc2x0 C. After this incubation period, the oil phase is separated and the enzyme complex is denatured preferably by heat. Typical times and temperatures are 20 minutes at 100xc2x0 C. or until the emulsion clears. Any particles which remain are filtered off.
When a purified lipase is used, an aqueous solution of the lipase is mixed with a suitable oil and the mixture is homogenized using stirring at high speed (i.e. 30,000 rpm) or other means of homogenization such as mixing in a blender or sonication. A Power Gen Homogenizer Model 1700 with a variable speed range of 10,000-30,000 rpm is available from Fisler Scientific. In this step, the ratio of the lipase or lipase mixture to the oil is important. If Validase 8000 fungal lipase is employed, 2 gm of the enzyme is mixed with 600 ml of water and stirred for 1 hour. The resulting enzyme solution is then added to 1 liter of sunflower oil, high oleic type, Optimum Quality Greens, LLC, Urbandale, Iowa, in a typical procedure. As set forth above, it appears that an optimum condition is a simple complex between the triglyceride and the lipase. The homogenized mixture is then incubated for a time and at a temperature sufficient to assure the association of the fatty acid or fatty ester components of the oil with the lipase. Typically, the incubation period is from 10-30 hours, preferably 15-27 hours, most preferably 24 hours and the temperature is elevated above room temperature, preferably 25-50xc2x0 C., more preferably 30-45xc2x0 C., and most preferably 40xc2x0 C. Optimum conditions appear to be 24 hours at 40xc2x0 C. Alterations of the incubation time and temperature are, however, possible since the time and temperature factors are interdependent.
After a suitable incubation period, the oil phase is separated and treated to denature the enzyme and stabilize the complex. Typical denaturation procedures include heat, typically at 95xc2x0 C. for about 10 minutes. Other denaturation procedures may, however, be used, such as microwaving, pH adjustment and chaotropic agents. During heat denaturation, the emulsion clears. The denaturation is necessary to prevent enzymic activity with respect to the linear alcohols that will be added later. Heat denaturation also removes water from the lipase structure. Water interferes in the surfactant addition performed later in the formulation. Further, the lipase will no longer be able to attach to new substrate. The emulsion separates into an oil and water bi-layer; the oil layer is retained and the water layer discarded. The water layer does not form an emulsion with new oil due to the heat denaturation process.
Once the denatured complex is stabilized, any solid particles that are present are removed by centrifugation or filtration or any other effective procedure. There may be no solid particles in some instances. Surfactants are then added to complete the formation of the active complex.
Saccharide/Fatty Acid Molecules
In another embodiment of the active ingredient, the complex comprises a saccharide, such as sucrose, sorbitol, xylitol, glucose, raffinose, or erythritol esterified to at least one fatty acid residue which is monounsaturated and contains 16-20 C, preferably 18 C (i.e., oleic acid). The saccharide core may be esterified to one or more than one, such as 2, 3, 4 or 5 fatty acids. At least one of the fatty acids must be of the appropriate size and unsaturation; as long as this is the case, other types of fatty acid backbones may also be included. It is preferred that the polyol saccharide cores be also derivatized with polyoxyalkylenes, in particular, polyoxyethylene. In addition to saccharide cores, other alcohols may also be used, such as glycerols, which may contain polyoxyalkylene chains as well. For example, ARCO Chemicals has commercialized esterified propoxylated glycerols. The Olestra(trademark) products of Procter and Gamble are sucrose polyesters containing fatty acids in the range of 8-22 carbons; to the extent that oleates or monounsaturated fatty acids in the C16-C20 range are included among these, these moieties are also useful in the invention. Particularly preferred is the commercially available material Toximul SEE-340, a sorbitan trioleate ethoxylate containing 20 moles of ethylene oxide. It may be advantageous, in this instance, to solubilize the Toximul SEE-340 initially in a mixture of aromatic hydrocarbons such as Exxon Aromatic 100. Other sorbitol esters and sorbitol ester ethoxylates can also be used. These are commonly referred to as SPANs, TWEENs, sorbac and polysorbac.
Addition of Surfactants
While not intending to be bound by any theory, in both embodiments above, it is believed that the long chain hydrophobic portion of the complex penetrates the lipid layers of the cells or membranes of the target pest, while the hydrophilic portion, preferably associated with an anionic detergent, becomes attached to the proteins embedded in the lipid layers. The effect is believed to be enhanced by the presence of shorter chain alcohols. Further, suitable detergents and ethoxylated alcohols permit an effective microemulsion and effective dispersion of the complex for application. In compositions where the active ingredient is a lipase associated with a fatty acid or derivative, polyoxyalkylene polymers are advantageously added in the form of the above-mentioned ethoxylated alcohols. This can be done in any composition of the invention. However, in those compositions where the moiety comprises a saccharide core esterified with fatty acids, polyoxyalkylene polymers may be derivatized directly to the core. In any case, a preferred form of polyoxyalkylene is polyoxyethylene.
Regardless of the nature of the active ingredient used, addition of surfactants is required in order to complete the effective complex. It appears that the order of addition of surfactants is important. In the case of hydrophobic/hydrophilic moieties where a polyoxyalkylene is already included, further addition of such polymers may be unnecessary. However, in the case of embodiments where the hydrophobic/hydrophilic moiety is a complex with denatured lipase, it is often necessary or desirable to include a source of such polyoxyalkylene polymers. Inclusion of additional such polymers may also be desirable even though the hydrophobic/hydrophilic moiety contains some level of such entities. In these cases, initially, an alkoxylated, typically ethoxylated, linear alcohol or alkoxylated/ethoxylated mixture of alcohols containing 9-11 carbons is added followed by homogenizing. This is optionally followed by adding an ethoxylated linear alcohol of 11 carbons, and then homogenizing. This is then followed by adding a surfactant blend for microemulsion formation and homogenizing, and finally an anionic surfactant is added. The final composition is then homogenized. By using appropriate concentrations, the resultant forms a concentrated premix which then can be diluted for application to agricultural crops.
Thus, in the first step described above, mixtures of linear alcohols of suitable chain lengths with an appropriate degree of alkoxylation can be used. The proportions of C9, C10 and C11 alcohols can be variable, but typically, the mixture contains at least 25 percent of C9 linear alcohols. Commercially available mixtures are typically ethoxylated to varying degrees, 2.5 moles of ethoxylation in the polymeric chain being preferred. Although ethoxylation is the most typical commercially available form, there is no theoretical reason that methoxylation or formation of polymeric ethers with higher chain alcohols could not be used. Tomah Reserve, Inc. markets a series of linear alcohols trademarked Tomadol(trademark). The Tomadol(trademark) compositions vary in chain length of the alcohol and number of moles of ethoxylation. For compositions where the alcohol contained 11 carbons, 7 moles of ethoxylation per mole of alcohol appeared optimal; 9 moles resulted in a solid at room temperature. Further, in compositions which contain mixtures of 9-11 carbon alcohols, 2.5 moles ethoxylation per mole of alcohol appeared to exhibit the best insect cuticle penetration.
Similarly, in the second (optional) step, C11 linear alcohols in ethoxylated form are also added. Typical levels of ethoxylation include 7 moles of monomer in the polymeric chain; as was the case with the ethoxylated mixture in the first step, other alkoxylated forms could be substituted.
In the third step, a surfactant blend for microemulsion formation is employed. Various commercial preparations are available, including those from Stepan Chemical Company, Winder, Ga. Of seven microemulsion formulations produced by Stepan Chemical, the highly preferred formulation is commercially designated H306A. The company will produce this formulation on special order of 20,000 lb. batches.
Microemulsion concentrate formulations such as are described by Skelton, P. R., xe2x80x9cPesticide Microemulsion Concentrate Formulations Utilizing Fatty Acid Methyl Esters as Solvent Alternatives,xe2x80x9d Pesticide Formulations and Application Systems: 13th Vol., ASTM STP 1183, Paul D. Berger, Bala N. Devisetty, and Franlin R. Hall, Eds, American Society for Testing and Materials, Philadelphia, 1993. Components can include combinations of the following: methyl esters, sorbitan ester ethoxylates, butoxy block copolymer, alkyl benzene sulfonic acid, and calcium salt. Alternatives for the ethoxylate and/or the block copolymer can be castor oil ethyoxylates. The foregoing are only examples, and the formulations are not limited to those components. Other microemulsion formulations are available.
In the fourth step, an anionic detergent or mixture of anionic detergents is used. Anionic surfactants, such as sodium lauryl sulfate and ammonium lauryl sulfate are known. In general, such surfactants include: alkylarylsulfonates, linear alkylbenzene sulfonates, alkane sulfonates, alcohol sulfates, alcohol ether sulfates, polyether carboxylates, olefin sulfonates, a-sulfomonocarboxylic esters, sulfosuccinates, phosphorus-containing anionics, and phosphate esters. Commercial mixtures are also available, although the variety of options available has decreased due to the introduction of siloxane-based surfactants now more commonly used in agriculture. However, anionic detergents are important in the compositions of the invention for several reasons. First, the anionic surfactant is believed to attach to the remainder of the lipase with which the oil, such as triolein, is associated. Anionic surfactants would associate, also, with the hydrophilic core in the case of sugar-based moieties. The result is that the complex, bearing a negative charge, will be more effective in binding nematode membranes in the soil. Second, in the case of acidic soils, additional anionic surfactant is desirable to neutralize the positive charges in the environment. One anionic surfactant currently marketed is Atsurf 1910 which, in its newer version at surf 1910 HF with a higher flash point, is less desirable that the version previously sold.
Typically, the composition is diluted 1:200, 1:500, 1:1000, or 1:2000 for application. The final concentration of the fatty acid backbone component is on the order of 200 ppm. The diluted composition must be clear and not turbid. Initially, is apparent that any dilution which does not appear clear to the naked eye should be rejected. It is preferable, however, that the turbidity of the final composition be less than 3 NTU, more preferably less than 2.5 NTU, and most preferably less than 1.0 NTU as measured in a turbidometer. The dilution may result in a satisfactorily clear solution without further agitation, or it may be necessary to stir, shake or vortex or otherwise agitate the dissolved components in order to effect clarity. Application of the solution can be by conventional means such as irrigation, spraying, and the like. Suitable target crops are any that are affected by undesired infestation by bacteria, fungi or nematodes, in particular by nematodes. The composition has been extensively tested on pineapple.
In somewhat more detail, the premix is diluted with additional surfactant and emulsifier, if desired, to the requisite dilution. The dilution is determined by the extent of infestation, the nature of the crop, and its stage of development. After dilution to form an additional clear microemulsion as described above, the diluted material is applied to the surface of the plots containing the plants. If desired, observations of the effectiveness of the pesticide may be taken systematically. Such observations may include the health of the plant generally, or may also involve specific measurement of pest viability. As exemplified below, suitable dilutions were able to lower nematode viability on pineapple crops to a very low level.
Soil moisture levels are important. If the soil is water saturated, the solution will not penetrate the soil particles and effectiveness drops. Thus, if it rains and the soil becomes soggy, it is preferred to delay application. Similarly, if a large amount of water is added as a post wet treatment, the effects may be diluted. Rains after application may also affect effectiveness. Larger or more concentrated dosages will kill within 1 day, some of the stronger formulations will kill 100% in 45 minutes of exposure. Weaker formulations may take several days to reach the same effectiveness.
The particular choice of formulation and the level of dilution may also determine the level and type of possible side effects on plant growth and health. In some formulations on some plants, growth is enhanced in addition to effecting nematode control. In some cases, the formulations may be slightly inhibitory or toxic. In general, the preparations which include fungal digested oil in relatively high concentrations are best used on pineapples as target crops and work less effectively, when taken in terms of total effect, on tomatoes. However, these aspects are independent of the nematode control aspects of the formulation and the formulations and dilution levels can readily be optimized for any particular type of plant.
The more general carrier formulations of the invention are designed to assist dispersal and penetration of active ingredients such as pesticides or drugs. However, in some instances, the invention compositions may themselves have applicability as pesticides where membrane disruption is the only requirement for effectiveness. Further, the compositions with or without active ingredients may be used as formulated, or, especially with respect to application to crops, may be diluted in water, often to a vary high degreexe2x80x94i.e., dilutions of 1:10, 1:100, 1:1,000 or 1:10,000 may be acceptable depending on the context. In all cases, for maximum effectiveness, the final formulation should appear clear to the naked eye. If the turbidity is measured with instrumentation, it is preferred that the turbidity be less than 5 NTU, more preferably less than 3 NTU, and most preferably less than 1 NTU.
The composition""s three essential components can further be described as follows:
The first component is a linear alcohol containing 7-12 C, preferably 9-11 C which is derivatized with a polyalkoxylene moiety, such as polyethylene oxide. Of course, mixtures of such linear alcohols can be used. The variables in this component include the number of carbons in the linear alcohol and the number and nature of alkoxylene units in the polyalkoxylation. Generally, mixtures containing approximately equal amounts of alcohols containing 9-11 carbons is preferred, although a preponderance of C11 alcohols, especially where the polyalkoxylene ratio is relatively highxe2x80x94i.e., on the order of 5-9, may be included within this mixture or added subsequently. It is not necessary to include a mixture of such alcohols and a single, for example, C10 alcohol could be used. The degree of polyethoxylation or polyalkoxylation is also acceptable within a range; in general, the majority of the alcohols should be polyalkoxylated in a ratio of 2-6 alkoxylene units is preferred. For practical reasons, polyethoxylene is the preferred polyalkoxylenexe2x80x94thus it is possible, in a preferred embodiment, to consider the linear alcohols xe2x80x9cPEGylated.xe2x80x9d
The degree of polyalkoxylation that is optimum for a particular composition will depend on the nature of the alkoxylene in the polymer, the chain length of the linear alcohol, and the nature of the remaining polyalkoxylated alcohols in any mixture that might be used. In a typical formulation, a mixture of C9-C11 linear alcohols at a PEGylation ratio of 2.5 moles of ethylene glycol per linear alcohol is used, supplemented with a C10 or C11 PEGylated alcohol at a ratio of 6-8, preferably 7 moles of ethylene glycol per linear alcohol unit.
The alkoxylation ratio describes the ratio of alkoxylene units to linear alcohol. The ratio may represent an averagexe2x80x94i.e., not all of the molecules in the mixture may show the same ratio.
Polyalkoxylated alcohols suitable for inclusion in the compositions of the invention may be formulated independently or are commercially available. For example, Tomah Reserve, Inc. markets such mixtures.
The second required component is a surfactant or mixture of surfactants which promotes microemulsion formation. Typically, the surfactants included in this component are nonionic and amphiphilic. Microemulsion formation is apparently best promoted by mixtures of such surfactants. Suitable components of such mixtures include such nonionic surfactants as esterified phospholipids and sorbitol esters with long chain fatty acids. Suitable mixtures can be formulated independently and are also commercially available, for example, from the Stepan Chemical Co., Winder, Ga.
The third component is an anionic detergent, such as the ammonium and metal salts of sulfonated fatty acids. Suitable anionic detergents include, for example, ammonium and sodium lauryl sulfate, aromatic sulfonic acid salts, and the like.
Optimum results in terms of encouraging dispersal and penetration are obtained when the components of the mixture are added in the order listed above with mixing after each step. Thus, the microemulsion-enhancing surfactant is added to the polyalkoxylated linear alcohol component(s) and thoroughly blended prior to the addition of the anionic detergent. In all cases, suitable agitation and mixing are required. The ratios of the components can vary, but it is preferred to include about 1-5 parts polyalkoxylated linear alcohol to about 9-15 parts microemulsion enhancer to about 9-15 parts anionic detergent. Particularly preferred ratios of components comprise about 5-7 parts polyalkoxylated alcohols to 11-13 parts microemulsion enhancer to about 11-13 parts anionic detergent. A particularly preferred ratio is 7:12:12.
The final form of formulation which includes the compositions of the invention depends on the nature of the application. For pharmaceutical applications and topical drug delivery, preferably the composition containing an active ingredient is applied in undiluted form. The active ingredient or active ingredients can be added directly to the composition or, alternatively, the composition can be built around the active ingredients. Any pharmaceutically active compound is an appropriate active ingredient, including small molecule pharmaceuticals, proteins, antiviral agents, antibiotics, anti-inflammatory agents, beta blockers, and the like. The reader is referred, for example, to the current edition of the Physician""s Desk Reference, incorporated herein by reference.
For a pharmaceutical use, additional components may be added to the final formulation so long as they do not distort the dispersant/penetrant qualities of the carrier composition of the invention. For example, antioxidants, stabilizers, and salts for controlling pH may be added to the formulation. Small amounts of diluent may also be included.
For agricultural applications, although the compositions may be used per se as, for example, nematocides by virtue of their ability to disrupt membranes, typically, they are supplied with an additional active ingredient such as an herbicide, pesticide or nutrient. Because of the requirement to provide the active ingredient over a wide area, the final formulation is typically diluted. Quite large dilution ratios are frequently employed so that the active ingredient is present only in 100-500 ppm, for example. Typical active ingredients include cytokinins, auxins, gibberellic esters, indole acetic acid, and similar compounds. Preferred compounds include zeatin, gibberellic acid, and abseisic acid. Also included are pesticides including synthetic and biological-based pesticides and, in appropriate cases, herbicides.
In all cases, the final formulation should be clear to the naked eye. Preferably, the final formulation has a turbidity of less than 5 NTU, and more preferably less than 1 NTU.
In one preferred preparation, initially, an alkoxylated, typically ethoxylated, linear alcohol or alkoxylated/ethoxylated mixture of alcohols containing 9-11 carbons is added to one or more active ingredients followed by homogenizing. This is optionally followed by adding an ethoxylated linear alcohol of 11 carbons, and then homogenizing. This is then followed by adding a surfactant blend for microemulsion formation and homogenizing, and finally an anionic surfactant is added. The final composition is then homogenized. By using appropriate concentrations, the resultant forms a concentrated premix which then can be diluted for application to agricultural crops, or, if the active ingredient is a drug, may be used in undiluted form.
Thus, in the first step described above, mixtures of linear alcohols of suitable chain lengths with an appropriate degree of alkoxylation can be used. The proportions of C9, C10 and C11, alcohols can be variable, but typically, the mixture contains at least 25 percent of C9 linear alcohols. Commercially available mixtures are typically ethoxylated to varying degrees, 2.5 moles of ethoxylation in the polymeric chain being preferred. Although ethoxylation is the most typical commercially available form, there is no theoretical reason that methoxylation or formation of polymeric ethers with higher chain alcohols could not be used. Tomah Reserve, Inc. markets a series of linear alcohols trademarked Tomadol(trademark). The Tomadol(trademark) compositions vary in chain length of the alcohol and number of moles of ethoxylation. For compositions where the alcohol contains 11 carbons, 7 moles of ethoxylation per mole of alcohol appears optimal; 9 moles can result in a solid at room temperature. Further, in compositions which contain mixtures of 9-11 carbon alcohols, 2.5 moles ethoxylation per mole of alcohol appears to exhibit the best insect cuticle penetration.
In the second optional step, C11 linear alcohols in ethoxylated form are also available. Typical levels of ethoxylation include 7 moles of monomer in the polymeric chain; as was the case with the ethoxylated mixture in the first step, other alkoxylated forms could be substituted.
In the third step, a surfactant blend for microemulsion formation is employed. Various commercial preparations are available, including those from Stepan Chemical Company, Winder, Ga. Of seven microemulsion formulations produced by Stepan Chemical, the highly preferred formulation is commercially designated H306A. The company will produce this formulation on special order of 20,000 lb. batches.
In the fourth step, an anionic detergent or mixture of anionic detergents is used. Anionic surfactants, such as sodium lauryl sulfate and ammonium lauryl sulfate are known. Commercial mixtures are also available, although the variety of options available has decreased due to the introduction of siloxane-based surfactants now more commonly used in agriculture. However, anionic detergents are required in the compositions of the invention. One anionic surfactant currently marketed is Atsurf 1910 which, in its newer version Atsurf 1910 HF with a higher flash point, is less desirable that the version previously sold.
For agricultural uses, the composition is diluted 1:200, 1:500, 1:1000, or 1:2000 for application. The final concentration of the active ingredient is on the order of 200 ppm. The diluted composition must be clear and not turbid. Any dilution which does not appear clear to the naked eye should be rejected. It is preferable, however, that the turbidity of the final composition be less than 3 NTU, more preferably less than 2.5 NTU, and most preferably less than 1.0 NTU as measured in a turbidometer. The dilution may result in a satisfactorily clear solution without further agitation, or it may be necessary to stir, shake or vortex or otherwise agitate the dissolved components in order to affect clarity.
The following examples are intended to illustrate but not to limit the invention.